pharmacy practice 1 dr. muslim suardi, msi., apt. faculty of pharmacy university of andalas emulsion

Pharmacy Pharmacy Practice 1Practice 1

Dr. Muslim Suardi, MSi., Apt. Dr. Muslim Suardi, MSi., Apt. Faculty of Pharmacy University of Faculty of Pharmacy University of AndalasAndalas

Emulsion

EmulsionEmulsion

““A thermodynamically unstable A thermodynamically unstable two-phase system consisting of at two-phase system consisting of at least least two immiscible liquidstwo immiscible liquids, one , one of which is dispersed in the form of which is dispersed in the form of small droplets throughout the of small droplets throughout the other, & an other, & an emulsifying agentemulsifying agent” ”

An emulsion is a thermodynamically unstable two-phase system consisting of at least two immiscible liquids, one of which is dispersed in the form of small droplets throughout the other, and an emulsifying agent. The dispersed liquid is known as the internal or discontinuous phase, whereas the dispersion medium is known as the external or continuous phase. Where oils, petroleum hydrocarbons, and/or waxes are the dispersed phase, and water or an aqueous solution is the continuous phase, the system is called an oil-in-water (o/w) emulsion. An o/w emulsion is generally formed if the aqueous phase constitutes > 45% of the total weight, and a hydrophilic emulsifier is used. Conversely, where water or aqueous solutions are dispersed in an oleaginous medium, the system is known as a water-in-oil (w/o) emulsion. W/O emulsions are generally formed if the aqueous phase constitutes < 45% of the total weight and an lipophilic emulsifier is used.

Phase of EmulsionPhase of Emulsion

Internal phaseInternal phase

Discontinuous phase: Discontinuous phase:

Dispersed liquid Dispersed liquid

External phaseExternal phase

Continuous phase: Continuous phase:

Dispersion medium Dispersion medium

Oil-in-Water EmulsionOil-in-Water Emulsion

Dispersed phase: Oils, petroleum Dispersed phase: Oils, petroleum hydrocarbons, waxeshydrocarbons, waxes

Continuous phase: water or an Continuous phase: water or an aqueous solution. aqueous solution.

O/W emulsion: generally formed if O/W emulsion: generally formed if the aqueous phase constitutes > the aqueous phase constitutes > 45% of the total weight, & a 45% of the total weight, & a hydrophilic emulsifier is used. hydrophilic emulsifier is used.

Water-in-Oil EmulsionWater-in-Oil Emulsion

Water or aqueous solutions are Water or aqueous solutions are dispersed in an oleaginous medium. dispersed in an oleaginous medium.

Generally formed if the aqueous Generally formed if the aqueous phase constitutes <45% of the total phase constitutes <45% of the total weight & an lipophilic emulsifier is weight & an lipophilic emulsifier is used.used.

Usage of EmulsionsUsage of Emulsions

Many routes of administration. Many routes of administration. Oral administration can be used, but Oral administration can be used, but

patients generally object to the oily patients generally object to the oily feel of emulsions in the mouth. feel of emulsions in the mouth.

Some times, emulsions are choosed Some times, emulsions are choosed to mask the taste of a very bitter to mask the taste of a very bitter drug or when the oral solubility or BA drug or when the oral solubility or BA of a drug is to be dramatically of a drug is to be dramatically increasedincreased

Topical EmulsionsTopical Emulsions

Creams: Creams: Have emollient properties. Have emollient properties. Can be o/w or w/o & are generally Can be o/w or w/o & are generally

opaque, thick liquids or soft solids. opaque, thick liquids or soft solids. Emulsions are also the bases used Emulsions are also the bases used

in lotions, as are suspensions. in lotions, as are suspensions.

LotionLotion

Not an official term, but is most Not an official term, but is most often used to describe fluid often used to describe fluid liquids intended for topical use. liquids intended for topical use.

Lotions have a lubricating effect. Lotions have a lubricating effect. Intended to be used in areas Intended to be used in areas

where the skin rubs against itself where the skin rubs against itself such as between the fingers, such as between the fingers, thighs, & under the arms.thighs, & under the arms.

Usage of EmulsionsUsage of Emulsions

Also used a ointment bases & IV-Also used a ointment bases & IV-ly administered as part of ly administered as part of parenteral nutrition therapy. parenteral nutrition therapy.

Their formulation & uses in these Their formulation & uses in these roles will be covered in the roles will be covered in the appropriate chapters.appropriate chapters.

Consistency of Consistency of Emulsions Emulsions

Varies from easily pourable Varies from easily pourable liquids to semisolid creams. liquids to semisolid creams.

Consistency will depend upon:Consistency will depend upon:

Internal phase volume to external Internal phase volume to external phase volume ratio in which phase volume ratio in which phase ingredients solidify what phase ingredients solidify what ingredients are solidifyingingredients are solidifying

Vanishing CreamsVanishing Creams

Stearic acid creams are o/w emulsions Stearic acid creams are o/w emulsions & have a semisolid consistency but are & have a semisolid consistency but are only 15% internal phase volume. only 15% internal phase volume.

Many emulsions have internal phases Many emulsions have internal phases that account for 40% - 50% of the total that account for 40% - 50% of the total volume of the formulation. volume of the formulation.

Any semisolid character with w/o Any semisolid character with w/o emulsions generally is attributable to a emulsions generally is attributable to a semisolid external phasesemisolid external phase

W/O Emulsions W/O Emulsions

Tend to be immiscible in water, not Tend to be immiscible in water, not water washable, will not absorb water, water washable, will not absorb water, are occlusive, & may be "greasy." are occlusive, & may be "greasy."

This is primarily because oil is the This is primarily because oil is the external phase, & oil will repel any of external phase, & oil will repel any of the actions of water. the actions of water.

Occlusiveness is because the oil will Occlusiveness is because the oil will not allow water to evaporate from the not allow water to evaporate from the surface of the skin. surface of the skin.

O/W Emulsions O/W Emulsions

Miscible with water, are water Miscible with water, are water washable, will absorb water, are washable, will absorb water, are nonocclusive, & are nongreasy. nonocclusive, & are nongreasy.

Water is the external phase & will Water is the external phase & will readily associate with any of the readily associate with any of the actions of wateractions of water

Emulsions InstabilityEmulsions Instability

By nature, physically unstable By nature, physically unstable Tend to separate into 2 distinct Tend to separate into 2 distinct

phases or layers over time. phases or layers over time.

InstabilityInstability

Creaming:Creaming:

Dispersed oil droplets merge & Dispersed oil droplets merge & rise to the top of an o/w emulsion rise to the top of an o/w emulsion or settle to the bottom in w/o or settle to the bottom in w/o emulsions. emulsions.

Emulsion can be easily Emulsion can be easily redispersed by shaking. redispersed by shaking.

InstabilityInstability

CoalescenceCoalescence

Breaking or cracking: complete & Breaking or cracking: complete & irreversible separation & fusion of irreversible separation & fusion of the dispersed phase. the dispersed phase.

Phase inversionPhase inversion

CChange from w/o to o/w (or vice hange from w/o to o/w (or vice versa) may occur. versa) may occur.

Emulsifying AgentsEmulsifying Agents

Emulsions are stabilized by adding an Emulsions are stabilized by adding an emulsifier. emulsifier.

Have a hydrophilic & a lipophilic part in their Have a hydrophilic & a lipophilic part in their chemical structure. chemical structure.

All emulsifying agents concentrate at & are All emulsifying agents concentrate at & are adsorbed onto the oil:water interface to adsorbed onto the oil:water interface to provide a protective barrier around the provide a protective barrier around the dispersed droplets. dispersed droplets.

In addition to this protective barrier, In addition to this protective barrier, emulsifiers stabilize the emulsion by reducing emulsifiers stabilize the emulsion by reducing the interfacial tension of the system. the interfacial tension of the system.

Emulsifying AgentsEmulsifying Agents

Enhancing stability by imparting a Enhancing stability by imparting a charge on the droplet surface thus charge on the droplet surface thus reducing the physical contact reducing the physical contact between the droplets & decreasing between the droplets & decreasing the potential for coalescence. the potential for coalescence.

Commonly used: tragacanth, Na Commonly used: tragacanth, Na lauryl sulfate, Na dioctyl lauryl sulfate, Na dioctyl sulfosuccinate, & polymers known as sulfosuccinate, & polymers known as the Spans® & Tweens®.the Spans® & Tweens®.

Emulsifyer Emulsifyer Classification Classification

Chemical structure: synthetic, Chemical structure: synthetic, natural, finely dispersed solids, & natural, finely dispersed solids, & auxiliary agents. auxiliary agents.

Mechanism of action: Mechanism of action: monomolecular, multimolecular, monomolecular, multimolecular, & solid particle films. & solid particle films.

Emulsifier Emulsifier RequirementRequirement

Regardless of their classification, Regardless of their classification, all emulsifiers must be chemically all emulsifiers must be chemically stable, inert & chemically non-stable, inert & chemically non-reactive with other emulsion reactive with other emulsion components, nontoxic & components, nontoxic & nonirritant. nonirritant.

They should also be reasonably They should also be reasonably odorless & not cost prohibitiveodorless & not cost prohibitive

Synthetic EmulsifiersSynthetic Emulsifiers

CationicCationic Anionic Anionic NonionicNonionic

Synthetic EmulsifiersSynthetic Emulsifiers

Cationic & anionic surfactants are Cationic & anionic surfactants are generally limited to use in topical, generally limited to use in topical, o/w emulsions. o/w emulsions.

Cationic:Cationic:

Benzalkonium chlorideBenzalkonium chloride

Benzethonium chlorideBenzethonium chloride

CationicCationic AgentsAgents

Quarternary ammonium salts Quarternary ammonium salts Incompatible with organic anions Incompatible with organic anions Infrequently used as emulsifiers. Infrequently used as emulsifiers.

Soaps are subject to hydrolysis & Soaps are subject to hydrolysis & may be less desirable than the may be less desirable than the more stable detergents.more stable detergents.

AnionicAnionic

Alkali soaps: Alkali soaps:

Na or K oleate Na or K oleate Amine soaps Amine soaps

TEA stearate; Detergents: Na TEA stearate; Detergents: Na lauryl sulfate, Na dioctyl lauryl sulfate, Na dioctyl sulfosuccinate, Na docusate).sulfosuccinate, Na docusate).

NonionicNonionic

Sorbitan esters (Spans®) Sorbitan esters (Spans®) Polyoxyethylene derivatives of Polyoxyethylene derivatives of

sorbitan esters (Tweens®) sorbitan esters (Tweens®) Glyceryl estersGlyceryl esters

Natural EmulsifierNatural Emulsifier

A variety of emulsifiers are A variety of emulsifiers are natural products derived from natural products derived from plant/animal tissue. plant/animal tissue.

Most of the emulsifiers form Most of the emulsifiers form hydrated lyophilic colloids hydrated lyophilic colloids (called hydrocolloids) that form (called hydrocolloids) that form multimolecular layers around multimolecular layers around emulsion droplets. emulsion droplets.

Hydrocolloid Hydrocolloid Emulsifiers Emulsifiers

Have little/no effect on interfacial Have little/no effect on interfacial tension, but exert a protective tension, but exert a protective colloid effect, reducing the potential colloid effect, reducing the potential for coalescence, by:for coalescence, by:

Providing a protective sheath around the Providing a protective sheath around the dropletsdroplets

Imparting a charge to the dispersed droplets (so Imparting a charge to the dispersed droplets (so that they repel each other)that they repel each other)

Swelling to increase the viscosity of the system Swelling to increase the viscosity of the system (so that droplets are less likely to merge)(so that droplets are less likely to merge)

Classification of Classification of Hydrocolloid Hydrocolloid EmulsifiersEmulsifiers

Vegetable derivatives: acacia, Vegetable derivatives: acacia, tragacanth, agar, pectin, tragacanth, agar, pectin, carrageenan, lecithincarrageenan, lecithin

Animal derivatives: gelatin, Animal derivatives: gelatin, lanolin, cholesterollanolin, cholesterol

Semi-synthetic agents: Semi-synthetic agents: methylcellulose, CMCmethylcellulose, CMC

Synthetic agents: Carbopols®Synthetic agents: Carbopols®

Naturally Plant Naturally Plant Hydrocolloids Hydrocolloids

Advantages: inexpensive, easy to Advantages: inexpensive, easy to handle, & nontoxic. handle, & nontoxic.

Disadvantages: require relatively large Disadvantages: require relatively large quantities to be effective as quantities to be effective as emulsifiers, subject to microbial emulsifiers, subject to microbial growth & thus their formulations growth & thus their formulations require a preservative. require a preservative.

Vegetable derivatives are generally Vegetable derivatives are generally limited to use as o/w emulsifiers.limited to use as o/w emulsifiers.

The Animal Derivatives The Animal Derivatives

General form w/o emulsions. General form w/o emulsions. Lecithin & cholesterol form a Lecithin & cholesterol form a

monomolecular layer around the monomolecular layer around the emulsion droplet instead of the emulsion droplet instead of the typically multimolecular layers. typically multimolecular layers.

Cholesterol is a major constituent of Cholesterol is a major constituent of wool alcohols & it gives lanolin the wool alcohols & it gives lanolin the capacity to absorb water & form a capacity to absorb water & form a w/o emulsion. w/o emulsion.

LecithinLecithin

A phospholipid derived from egg yolkA phospholipid derived from egg yolk Produces o/w emulsions because of Produces o/w emulsions because of

its strong hydrophilic character. its strong hydrophilic character. Animal derivatives are more likely to Animal derivatives are more likely to

cause allergic reactions & are subject cause allergic reactions & are subject to microbial growth & rancidity. to microbial growth & rancidity.

Advantage: in their ability to support Advantage: in their ability to support formation of w/o emulsionsformation of w/o emulsions

Semi-syntheticSemi-synthetic AgentsAgents

Stronger emulsifiers, nontoxic, & Stronger emulsifiers, nontoxic, & less subject to microbial growth. less subject to microbial growth.

Synthetic hydrocolloids: strongest Synthetic hydrocolloids: strongest emulsifiers, nontoxic, not support emulsifiers, nontoxic, not support microbial growth. microbial growth.

Cost may be prohibitive. Cost may be prohibitive. Generally limited to use as o/w Generally limited to use as o/w

emulsifiers.emulsifiers.

NaturalNatural EmulsifiersEmulsifiers

Derived from plant or animal Derived from plant or animal tissue. tissue.

Most of them form hydrated Most of them form hydrated lyophilic colloids lyophilic colloids (called hydrocolloids) that form (called hydrocolloids) that form multimolecular layers around multimolecular layers around emulsion droplets. emulsion droplets.

HydrocolloidHydrocolloid EmulsifiersEmulsifiers

Little/no effect on interfacial Little/no effect on interfacial tension, but exert a protective tension, but exert a protective colloid effect, reducing the colloid effect, reducing the potential for coalescence, by:potential for coalescence, by:

Providing a protective sheath around the droplets Providing a protective sheath around the droplets Imparting a charge to the dispersed droplets (so that Imparting a charge to the dispersed droplets (so that

they repel each other)they repel each other) Swelling to increase the viscosity of the system (so Swelling to increase the viscosity of the system (so

that droplets are less likely to merge)that droplets are less likely to merge)

Hydrocolloid Hydrocolloid Emulsifiers Emulsifiers

ClassificationClassification Vegetable derivatives: acacia, Vegetable derivatives: acacia,

tragacanth, agar, pectin, tragacanth, agar, pectin, carrageenan, lecithincarrageenan, lecithin

Animal derivatives: gelatin, lanolin, Animal derivatives: gelatin, lanolin, cholesterolcholesterol

Semi-synthetic agents: Semi-synthetic agents: Methylcellulose, CMCMethylcellulose, CMC

Synthetic agents, e.g., Carbopols®Synthetic agents, e.g., Carbopols®

PlantPlant HydrocolloidsHydrocolloids

Advantages Advantages

Inexpensive, easy to handle, & nontoxic. Inexpensive, easy to handle, & nontoxic. DisadvantagesDisadvantages

Require relatively large quantities to be Require relatively large quantities to be effective as emulsifierseffective as emulsifiers

Subject to microbial growth, require a Subject to microbial growth, require a preservative. preservative.

Generally limited to use as o/w emulsifiers.Generally limited to use as o/w emulsifiers.

AnimalAnimal DerivativesDerivatives

General form w/o emulsions. General form w/o emulsions. Lecithin & cholesterol form a Lecithin & cholesterol form a

monomolecular layer around the monomolecular layer around the emulsion droplet instead of the emulsion droplet instead of the typically multimolecular layers. typically multimolecular layers.

Cholesterol: a major constituent of Cholesterol: a major constituent of wool alcohols & it gives lanolin the wool alcohols & it gives lanolin the capacity to absorb water & form a capacity to absorb water & form a w/o emulsion. w/o emulsion.

LecithinLecithin

A phospholipid derived from egg yolk A phospholipid derived from egg yolk Produces o/w emulsions because of Produces o/w emulsions because of

its strong hydrophilic character. its strong hydrophilic character. Animal derivatives are more likely to Animal derivatives are more likely to

cause allergic reactions & are subject cause allergic reactions & are subject to microbial growth & rancidity. to microbial growth & rancidity.

Advantage: ability to support Advantage: ability to support formation of w/o emulsions.formation of w/o emulsions.

Semi-syntheticSemi-synthetic AgentsAgents

Stronger emulsifiers, nontoxic, & Stronger emulsifiers, nontoxic, & less subject to microbial growth. less subject to microbial growth.

Synthetic hydrocolloids are the Synthetic hydrocolloids are the strongest emulsifiers, nontoxic, & strongest emulsifiers, nontoxic, & not support microbial growth. not support microbial growth.

Cost may be prohibitive. Cost may be prohibitive. These synthetic agents are generally These synthetic agents are generally

limited to use as o/w emulsifierslimited to use as o/w emulsifiers

Finely Dispersed Solid Finely Dispersed Solid Particle EmulsifiersParticle Emulsifiers

Finely Divided Solid Particle Finely Divided Solid Particle EmulsifiersEmulsifiers

Form a particulate layer around Form a particulate layer around dispersed particles. dispersed particles.

Most will swell in the dispersion Most will swell in the dispersion medium to increase viscosity & medium to increase viscosity & reduce the interaction between reduce the interaction between dispersed droplets. dispersed droplets.

Finely Dispersed Solid Finely Dispersed Solid Particle EmulsifiersParticle Emulsifiers

Most commonly they support the Most commonly they support the formation of o/w emulsions, but formation of o/w emulsions, but some may support w/o emulsions. some may support w/o emulsions.

Include: bentonite, veegum, Include: bentonite, veegum, hectorite, Mg(OH)2, Al(OH)3 & Mg hectorite, Mg(OH)2, Al(OH)3 & Mg trisilicate.trisilicate.

AuxilarryAuxilarry

Fatty acids: stearic acid, Fatty acids: stearic acid, Fatty alcohols: stearyl or cetyl Fatty alcohols: stearyl or cetyl alcoholalcohol

Fatty esters: glyceryl monostearateFatty esters: glyceryl monostearate

Serve to stabilize emulsions through Serve to stabilize emulsions through their ability to thicken the emulsion. their ability to thicken the emulsion. Have only weak emulsifying Have only weak emulsifying properties, always used in properties, always used in combination with other emulsifiers.combination with other emulsifiers.

HLB SystemHLB System Hydrophile-lipophile Balance SystemHydrophile-lipophile Balance System A system was developed to assist in A system was developed to assist in

making systemic decisions about the making systemic decisions about the amounts & types of surfactants amounts & types of surfactants needed in stable products. needed in stable products.

Has an arbitrary scale of 1 - 18. Has an arbitrary scale of 1 - 18. HLB numbers are experimentally HLB numbers are experimentally

determined for the different determined for the different emulsifiers emulsifiers

HLB SystemHLB System

If an emulsifier has a low HLB If an emulsifier has a low HLB number, there is a low number of number, there is a low number of hydrophilic groups on the molecule hydrophilic groups on the molecule and it will have more of a lipophilic and it will have more of a lipophilic character. character.

Ex: Spans® generally have low HLB Ex: Spans® generally have low HLB numbers & they are also oil soluble. numbers & they are also oil soluble. They will cause the oil phase to They will cause the oil phase to predominate & form an w/o emulsion.predominate & form an w/o emulsion.


The higher HLB number would indicate The higher HLB number would indicate that the emulsifier has a large number that the emulsifier has a large number of hydrophilic groups on the molecule of hydrophilic groups on the molecule

More hydrophilic in character. More hydrophilic in character. Tweens® have higher HLB numbers & Tweens® have higher HLB numbers &

also water soluble. also water soluble. They will cause the water phase to They will cause the water phase to

predominate & form an o/w emulsion.predominate & form an o/w emulsion.

The higher HLB number would indicate that the emulsifier has a large number of hydrophilic groups on the molecule and therefore should be more hydrophilic in character. The Tweens ® have higher HLB numbers and they are also water soluble. Because of their water soluble character, Tweens® will cause the water phase to predominate and form an o/w emulsion.


Combinations of emulsifiers can Combinations of emulsifiers can produce more stable emulsions produce more stable emulsions than using a single emulsifier with than using a single emulsifier with the same HLB number. The HLB the same HLB number. The HLB value of a combination of value of a combination of emulsifiers can be calculated as emulsifiers can be calculated as follows:follows:

ExcercisesExcercises

What is the HLB value of a surfactant system composed of 20 g Span 20 (HLB = 8.6) + 5 g Tween 21 (HLB = 13.3)?

Methods of Emulsion Methods of Emulsion PreparationPreparation

Commercially, emulsions are Commercially, emulsions are prepared in large volume mixing prepared in large volume mixing tanks & refined & stabilized by tanks & refined & stabilized by passage through a colloid mill or passage through a colloid mill or homogenizer. homogenizer.

Extemporaneous production is Extemporaneous production is more concerned with small scale more concerned with small scale methods. methods.

Methods of Emulsion Methods of Emulsion PreparationPreparation

Several methods are generally Several methods are generally available to the pharmacist. Each available to the pharmacist. Each method requires that method requires that energyenergy be be put into the system in some form. put into the system in some form.

The energy is supplied in a The energy is supplied in a variety of ways: trituration, variety of ways: trituration, homogenization, agitation, & homogenization, agitation, & heat.heat.

Continental MethodContinental Method

Dry Gum, or 4:2:1 Method Dry Gum, or 4:2:1 Method Used to prepare the initial or primary Used to prepare the initial or primary

emulsion from oil, water, & a hydrocolloid emulsion from oil, water, & a hydrocolloid or "gum" type emulsifier (usually acacia). or "gum" type emulsifier (usually acacia).

The primary emulsion, or emulsion The primary emulsion, or emulsion nucleus, is formed from 4:2:1 parts of nucleus, is formed from 4:2:1 parts of oil:water:emulsifier. 4 parts oil & 1 part oil:water:emulsifier. 4 parts oil & 1 part emulsifier represent their total amounts emulsifier represent their total amounts for the final emulsion.for the final emulsion.


In a mortar, the 1 part gum is In a mortar, the 1 part gum is levigated with the 4 parts oil until the levigated with the 4 parts oil until the powder is thoroughly wettedpowder is thoroughly wetted

2 parts water are added all at once, & 2 parts water are added all at once, & the mixture is vigorously continually the mixture is vigorously continually triturated until the primary emulsion triturated until the primary emulsion formed is creamy white & produces a formed is creamy white & produces a "crackling" sound as it is triturated, "crackling" sound as it is triturated, usually 3-4 minusually 3-4 min


Additional water or aqueous solutions Additional water or aqueous solutions may be incorporated after the primary may be incorporated after the primary emulsion is formed. emulsion is formed.

Solid substances: active ingredients, Solid substances: active ingredients, preservatives, color, flavors. Generally preservatives, color, flavors. Generally dissolved & added as a solution to the dissolved & added as a solution to the primary emulsion. primary emulsion.

Oil soluble substance: in small amounts, Oil soluble substance: in small amounts, may be incorporated directly into the may be incorporated directly into the primary emulsion. primary emulsion.


Any substance which might reduce the Any substance which might reduce the physical stability of the emulsion, such as physical stability of the emulsion, such as alcohol (which may precipitate the gum) alcohol (which may precipitate the gum) should be added as near to the end of the should be added as near to the end of the process as possible to avoid breaking the process as possible to avoid breaking the emulsion. emulsion.

When all agents have been incorporated, the When all agents have been incorporated, the emulsion should be transferred to a calibrated emulsion should be transferred to a calibrated vessel, brought to final volume with water, vessel, brought to final volume with water, then homogenized or blended to ensure then homogenized or blended to ensure uniform distribution of ingredients.uniform distribution of ingredients.

English (Wet Gum) English (Wet Gum) MethodMethod

Proportions of oil, water, & Proportions of oil, water, & emulsifier are the same (4:2:1), emulsifier are the same (4:2:1), but the order & techniques of but the order & techniques of mixing are different. mixing are different.

The 1 part gum is triturated with 2 The 1 part gum is triturated with 2 parts water to form a mucilage; parts water to form a mucilage; then the 4 parts oil is added slowly, then the 4 parts oil is added slowly, in portions, while triturating. in portions, while triturating.

English (Wet Gum) English (Wet Gum) MethodMethod

After all the oil is added, the mixture After all the oil is added, the mixture is triturated for several min to form is triturated for several min to form the primary emulsion. Then other the primary emulsion. Then other ingredients may be added as in the ingredients may be added as in the continental method. continental method.

It is more difficult to perform It is more difficult to perform successfully, especially with more successfully, especially with more viscous oils, but may result in a more viscous oils, but may result in a more stable emulsion.stable emulsion.

Bottle (Forbes) MethodBottle (Forbes) Method

May be used to prepare emulsions May be used to prepare emulsions of volatile oils, or oleaginous of volatile oils, or oleaginous substances of very low viscosities. substances of very low viscosities.

It is not suitable for very viscous It is not suitable for very viscous oils since they cannot be oils since they cannot be sufficiently agitated in a bottle. sufficiently agitated in a bottle.

This method is a variation of the This method is a variation of the dry gum method. dry gum method.


One part powdered acacia (or other One part powdered acacia (or other gum) is placed in a dry bottle & four gum) is placed in a dry bottle & four parts oil are added. parts oil are added.

The bottle is capped & thoroughly The bottle is capped & thoroughly shaken. shaken.

The required volume of water is The required volume of water is added all at once, the mixture is added all at once, the mixture is shaken thoroughly until the primary shaken thoroughly until the primary emulsion forms. emulsion forms.


It is important to minimize the It is important to minimize the initial amount of time the gum initial amount of time the gum and oil are mixed. The gum will and oil are mixed. The gum will tend to imbibe the oil, and will tend to imbibe the oil, and will become more waterproof.become more waterproof.


It is also effective in preparing an olive It is also effective in preparing an olive oil & lime water emulsion, which is self-oil & lime water emulsion, which is self-emulsifying. emulsifying.

In the case of lime water & olive oil, In the case of lime water & olive oil, equal parts of lime water & olive oil are equal parts of lime water & olive oil are added to the bottle & shaken. No added to the bottle & shaken. No emulsifying agent is used, but one is emulsifying agent is used, but one is formed "in situ" following a chemical formed "in situ" following a chemical interaction between the components. interaction between the components. What emulsifying agent is formed?What emulsifying agent is formed?

Beaker Method Beaker Method

When synthetic or non-gum When synthetic or non-gum emulsifiers are used, the proportions emulsifiers are used, the proportions given in the previous methods become given in the previous methods become meaningless. meaningless.

Most appropriate method for preparing Most appropriate method for preparing emulsions from surfactants or other emulsions from surfactants or other non-gum emulsifiers is to begin by non-gum emulsifiers is to begin by dividing components into water dividing components into water soluble & oil soluble componentssoluble & oil soluble components


All oil soluble components are All oil soluble components are dissolved in the oily phase in one dissolved in the oily phase in one beaker & all water soluble beaker & all water soluble components are dissolved in the components are dissolved in the water in a separate beaker. water in a separate beaker.

Oleaginous components are Oleaginous components are melted & both phases are heated melted & both phases are heated to ±70°C over a water bath. to ±70°C over a water bath.


The internal phase is then added The internal phase is then added to the external phase with stirring to the external phase with stirring until reaches room temperature. until reaches room temperature.

The mixing of such emulsions can The mixing of such emulsions can be carried out in a beaker, be carried out in a beaker, mortar, or blender; or, in the case mortar, or blender; or, in the case of creams & ointments, in the jar of creams & ointments, in the jar in which they will be dispensed. in which they will be dispensed.

AuxiliaryAuxiliary MethodsMethods

Instead of, or in addition to, any Instead of, or in addition to, any of the preceding methods, the of the preceding methods, the pharmacist can usually prepare pharmacist can usually prepare an excellent emulsion using an an excellent emulsion using an electric mixer or blender. electric mixer or blender.

AuxiliaryAuxiliary MethodsMethods

An emulsion prepared by other An emulsion prepared by other methods can also usually be methods can also usually be improved by passing it through a improved by passing it through a hand homogenizer, which forces hand homogenizer, which forces the emulsion through a very small the emulsion through a very small orifice, reducing the dispersed orifice, reducing the dispersed droplet size to about 5 µm or less.droplet size to about 5 µm or less.

HLBHLB ValuesValues

Commercial Name Chemical Name HLB Value

PEG 400 Monolaurate Polyoxyethylene monolaurate 13.1

Sodium lauryl SO4 Sodium lauryl SO4 40

Span® 20 Sorbitan monolaurate 8.6

Span® 60 Sorbitan monostearate 4.7

Span® 85 Sorbitan trioleate 1.8

TEA oleate TEA oleate 12

Tween® 20 Polyoxyethylene sorbitan monolaurate

16.7

Tween® 65 Polyoxyethylene sorbitan tristearate

10.5

pharmacy practice 1 dr. muslim suardi, msi., apt. faculty of pharmacy university of andalas emulsion

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